1. Field of the Invention
The present invention generally relates to vehicle suspension systems. More specifically, the present invention relates to vehicle suspension systems comprising hydraulic dampers interrelated through pressure regulators of reduced storage capacity.
2. Related Art
Land vehicles often comprise a chassis that is supported by a set of wheels. In some land vehicles, the chassis is supported by other members, such as skis or the like. The supporting members, whether they are wheels, skis or other configurations, often are connected to the chassis through a shock absorbing member. For instance, the chassis may be considered an unsprung mass while the supporting members comprise sprung members.
In a specific application, such as an automobile, the chassis is supported by a front right wheel, a front left wheel, a rear right wheel and a rear left wheel. The wheels are supported by springs and a shock absorber or other damping member extends between the wheel and the chassis. The purpose of the shock absorber or other damping member is to attenuate or slow the relative movement between the wheel and the chassis.
In some arrangements, the damping member of two or more wheels can be interrelated. By interrelating the damping members, the movement of the respective wheels can be used to impact the damping of each of the other interrelated wheels. For instance, in an ordinary interrelated configuration, a pair of hydraulic shock absorbers are connected through a pressure regulator. If the wheels are displaced in the same direction by approximately the same amount, then the shock absorbers provide the damping for the respective forces. If the wheels are otherwise displaced, then the shock absorbers and the pressure regulator provide the desired damping forces.
One known arrangement is illustrated rather schematically in FIG. 1. The illustrated arrangement comprises a right hydraulic damper 10 and a left hydraulic damper 12. The two hydraulic dampers 10, 12 are interrelated through a pressure regulator 14. Each hydraulic damper 10, 12 comprises a cylinder 16, 18 in which a piston 20, 22 is freely slideable. In the illustrated arrangement, the pistons 20, 22 are mounted to a top end the respective one of a set of piston rods 24, 26 The piston rods can be inserted from a lower end of the cylinders 16, 18 such that the piston rods 24, 26 would be fixed to the respective wheels and the cylinders 16, 18 would be fixed to the chassis.
The interior of the cylinders 16, 18 are divided with the respective pistons 20, 22 into upper oil chambers 28, 30 and lower oil chambers 32, 34, both of which preferably are filled with suitable fluid, such as oil for instance. The pistons 20, 22 each comprise at least one communication passage 36, 38, which are provided with corresponding throttles 40, 42. The passage 36 places the upper oil chamber 28 in communication with the lower oil chamber 32 and the passage 38 places the upper oil chamber 30 in communication with the lower oil chamber 34. The throttles 40, 42 control the flow rate between the respective chambers and generates the damping force for each of the dampers 10, 12.
As described above, the dampers 10, 12 are interrelated through a pressure regulator 14. In the illustrated arrangement, the pressure regulator 14 comprises a pair of mutually communicating cylinders 46, 48. A piston 50 is inserted in one of the cylinders 46 and a second piston 52 is inserted in the other of the cylinders 48. The two pistons 50, 52 are connected with a connecting rod 54. The connecting rod 54 assures that movement of one of the pistons 50, 52 will cause movement of the other of the pistons 50, 52.
The pistons 50, 52 divide the inside of the cylinders 46, 48 into a pair of upper chambers 56, 58 and a lower chamber 60. The upper chamber 56, 58 preferably are filled with the same fluid as is used in the hydraulic dampers 10, 12 while the lower chamber preferably is filled with an inert gas. As illustrated, the upper chambers 56, 58 are in fluid communication with at least one of the oil chambers of the respective dampers 10, 12.
Functionally, when the vehicle encounters bumps or other surface irregularities over which the vehicle is being operated, the piston rods 24, 26 either extend or contract with respect to the corresponding cylinder 16, 18. The movement of the piston rods 24, 26 causes a displacement of the pistons 20, 22 which slide inside the cylinders 16, 18 and which change the relative volumes of the associated upper chambers 28, 30 and the lower chambers 32, 34. As the pistons 20, 22 slide, oil passes through the throttles 40, 42 provided in the communication passage 36, 38 of the pistons 20, 22 to produce a damping force which attenuates oscillation of the vehicle chassis. Furthermore, an amount of oil in the cylinders 16, 18 is displaced by a volume defined by the associated piston rods 24, 26. The displaced oil is transferred through relief lines 62, 64 to the pressure regulator 14 where the change in the oil volume is balanced by the compression or expansion of the gas in the gas chamber 60 caused by the sliding movement of the free pistons 50, 52 of the pressure regulator 14.
In one configuration, one in which the diameter of the piston rod of each hydraulic damper is great, the amount of displaced oil caused by movement of the piston rod into and out of the cylinder is great. Thus, the pressure regulator must accommodate rather large volumes of oil. This results not only in the increase in size, weight and cost of the pressure regulator but also increases the difficulty associated with properly positioning and mounting the pressure regulator on the vehicle.
Accordingly, a vehicle suspension system is desired that reduces the overall size, weight and resultant cost of the pressure regulator and that increases the degree of freedom in positioning and mounting the pressure regulator on a vehicle.
Accordingly, one aspect of the present invention comprises a vehicle suspension system comprising a first hydraulic damper and a second hydraulic damper. The first hydraulic damper comprises a first inner cylinder and a first outer cylinder. The first inner cylinder and said first outer cylinder are arranged coaxially. The second hydraulic damper comprises a second inner cylinder and a second outer cylinder. The second inner cylinder and said second outer cylinder are arranged coaxially. A first piston rod is at least partially positioned within said first inner cylinder. A second piston rod is at least partially positioned within said second inner cylinder. A first sub-piston is at least partially disposed within said first piston rod. A first piston rod chamber is defined by at least a portion of said first piston rod and said first sub-piston rod. A second sub-piston is at least partially disposed within said second piston rod. A second piston rod chamber is defined by at least a portion of said second piston rod and said second sub-piston rod. A pressure regulator comprises a first chamber and second chamber with said first chamber being in fluid communication with said first piston rod chamber and said second chamber being in fluid communication with said second piston rod chamber.
Another aspect of the present invention involves a vehicle suspension system. The system comprises a first hydraulic damper comprising a first inner cylinder and a first outer cylinder. A first piston is slidably engaged in said first inner cylinder. A first hollow piston rod is connected to one end of said first piston. A first sub-piston rod and a first sub-piston formed on said first sub-piston rod are disposed at least partially within said first piston rod. A first elongate chamber is defined within said first piston rod. A second hydraulic damper comprises a second inner cylinder and a second outer cylinder. A second piston is slidably engaged in said second inner cylinder. A second hollow piston rod is connected to one end of said second piston. A second sub-piston rod and a second sub-piston formed on said second sub-piston rod are disposed at least partially within said second piston rod. A second elongate chamber is defined within said second piston rod. A pressure regulator comprises a first pressure chamber and a second pressure chamber. The first pressure chamber is connected to said first elongate chamber and the second pressure chamber is connected to said second elongate chamber.
A further aspect of the present invention involves a damper for a suspension system. The damper comprises an outer cylinder housing. A first chamber, a second chamber, and a third chamber are defined within said outer cylinder. The first chamber has a smaller volume than said second chamber and said third chamber. The third chamber extends around at least a portion of said second chamber and a valved passage places said second chamber and said third chamber in selective fluid communication with each other.
Yet another aspect of the present invention involves a damper comprising a cylinder and a piston slideably disposed within said cylinder. The piston divides said cylinder into an upper chamber and a lower chamber. A piston rod is connected to said piston and is at least partially positioned within said upper chamber. The piston rod comprises an axial passageway such that said piston rod is substantially hollow. A sub piston rod is at least partially disposed in said lower chamber and extends into said axial passageway of said piston rod. A sub piston is disposed along said piston rod. An elongate chamber is at least partially defined within said piston rod by said sub piston. A sub chamber is in fluid communication with said lower chamber.